The pharmacology of galanthamine and its analogues

Alkaloids as drug leads in Alzheimer's treatment: Mechanistic and therapeutic insights

Alzheimer's disease (AD) has few effective treatment options and continues to be a major global health concern. AD is a neurodegenerative disease that typically affects elderly people. Alkaloids have potential sources for novel drug discovery due to their diverse chemical structures and pharmacological activities. Alkaloids, natural products with heterocyclic nitrogen-containing structures, are considered potential treatments for AD. This review explores the neuroprotective properties of alkaloids in AD, focusing on their ability to regulate pathways such as amyloid-beta aggregation, oxidative stress, synaptic dysfunction, tau hyperphosphorylation, and neuroinflammation. The FDA has approved alkaloids such as acetylcholinesterase inhibitors like galantamine and rivastigmine. This article explores AD's origins, current market medications, and clinical applications of alkaloids in AD therapy. This review explores the development of alkaloid-based drugs for AD, focusing on pharmacokinetics, blood-brain barrier penetration, and potential adverse effects. Future research should focus on the clinical evaluation of promising alkaloids, developing recently discovered alkaloids, and the ongoing search for novel alkaloids for medical treatment. A pharmaceutical option containing an alkaloid may potentially slow down the progression of AD while enhancing its symptoms. This review highlights the potential of alkaloids as valuable drug leads in treating AD, providing a comprehensive understanding of their mechanisms of action and therapeutic implications.

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

Recent advances in the total synthesis of galantamine, a natural medicine for Alzheimer's disease

Covering: 2006 to 2023(-)-Galantamine is a natural product with distinctive structural features and potent inhibitory activity against acetylcholine esterase (AChE). It is clinically approved for the treatment of Alzheimer's disease. The clinical significance and scarcity of this natural product have prompted extensive and ongoing efforts towards the chemical synthesis of this challenging tetracyclic structure. The objective of this review is to summarize and discuss recent progress in the total synthesis of galantamine from 2006 to 2023. The contents are organized according to the synthetic strategies for the construction of the quaternary center. Key features of each synthesis have been highlighted, followed by a summary and outlook at the end.

Progress in approved drugs from natural product resources

Natural products (NPs) have consistently played a pivotal role in pharmaceutical research, exerting profound impacts on the treatment of human diseases. A significant proportion of approved molecular entity drugs are either directly derived from NPs or indirectly through modifications of NPs. This review presents an overview of NP drugs recently approved in China, the United States, and other countries, spanning various disease categories, including cancers, cardiovascular and cerebrovascular diseases, central nervous system disorders, and infectious diseases. The article provides a succinct introduction to the origin, activity, development process, approval details, and mechanism of action of these NP drugs.

Emerging Alzheimer's disease therapeutics: promising insights from lipid metabolism and microglia-focused interventions

More than 55 million people suffer from dementia, with this number projected to double every 20 years. In the United States, 1 in 3 aged individuals dies from Alzheimer's disease (AD) or another type of dementia and AD kills more individuals than breast cancer and prostate cancer combined. AD is a complex and multifactorial disease involving amyloid plaque and neurofibrillary tangle formation, glial cell dysfunction, and lipid droplet accumulation (among other pathologies), ultimately leading to neurodegeneration and neuronal death. Unfortunately, the current FDA-approved therapeutics do not reverse nor halt AD. While recently approved amyloid-targeting antibodies can slow AD progression to improve outcomes for some patients, they are associated with adverse side effects, may have a narrow therapeutic window, and are expensive. In this review, we evaluate current and emerging AD therapeutics in preclinical and clinical development and provide insight into emerging strategies that target brain lipid metabolism and microglial function - an approach that may synergistically target multiple mechanisms that drive AD neuropathogenesis. Overall, we evaluate whether these disease-modifying emerging therapeutics hold promise as interventions that may be able to reverse or halt AD progression.

ANTIMALARIAL activities and alkaloids from Crinum jagus (Thomps) DANDY

ETHNOPHARMACOLOGICAL RELEVANCE

Locally, among the Yoruba speaking people of South Western, Nigeria, the bulb of Crinum jagus (CJ), known as "ogede odo" is used to treat malaria and as an anthelmintic among other uses.

AIMS OF THIS STUDY

Study aimed at identifying the purified active fractions and constituents of this fraction in an antiplasmodial activity-guided process.

MATERIALS AND METHODS

Antiplasmodial activity-guided fractionation of the bulb and leaf extracts of CJ was investigated against chloroquine-sensitive (NK 65) Plasmodium berghei using 4-day suppressive and prophylactic methods. Molluscicidal activity of the extracts was assayed on adult Biomphalaria glabrata molluscs following WHO test protocols. Fractionation and purification of the active bulb extract was achieved using various chromatographic and spectroscopic techniques to isolate its constituents. Isolated compounds were identified using different spectroscopic methods.

RESULTS AND DISCUSSION

Both extracts had oral median lethal dose (LD₅₀) greater than 5000 mg/kg body weight (b.wt.). The leaf extract had 40% lethality on molluscs while the bulb extract was inactive. The chemosuppressive and prophylactic antimalarial effects of the bulb extract were 76.55 ± 2.76% and 90.49 ± 2.70% (p<0.05) respectively at 1000 mg/kg b. wt. while the reference drugs; chloroquine and pyrimethamine, had 80.26 ± 3.09% and 50.39 ± 6.80% chemosuppressive effects, respectively. Lycorine (1) and crinamine (2) were isolated from the alkaloidal fraction with 71.36 ± 12.54% antiplasmodial activity.

CONCLUSION

The leaf and bulb extracts of Crinum jagus displayed low molluscicidal and moderate antimalarial activities. Lycorine and crinamine were identified from the antiplasmodial alkaloidal active fraction of the bulb.

Pharmacokinetic and tissue distribution study of ZCY-15, a novel compound against Alzheimer's disease, in rats by liquid chromatography-tandem mass spectrometry

ZCY-15, N-(3,5-dimethyladamatan-1-yl)-N-(3-methylphenyl) urea, is a candidate compound synthesized from the memantine structure and has been shown to be remarkably effective in treating Alzheimer's disease. To elucidate the pharmacokinetics and tissue distribution of ZCY-15 in rats after oral and intravenous administration, a rapid and selective LC-MS/MS method was established for the determination of ZCY-15 in rat plasma and tissues. According to the dissolution characteristics, the plasma samples were prepared by acetonitrile protein precipitation and carbamazepine was selected as the internal standard (IS). After separation by gradient elution using Aqela Venusil ASB C₈ (2.1 × 50 mm, 3 µm), the pretreated samples were analyzed in MRM mode in positive ESI mode. The effective detection limit of this method was 1.95-1000 ng·mL^-1. Tissue samples were collected from the heart, liver, spleen, lung, kidney, fat, muscle, brain, hippocampus, testicles or ovaries, large intestine, small intestine and stomach. The proposed method demonstrated fine precision and accuracy for analyzing ZCY-15 in selected tissues within the concentration range of standard liquid chromatography-tandem mass spectrometry. The whole analysis time was 3.6 min per sample. After oral administration, the blood and tissue concentrations of ZCY-15 in female rats were significantly higher than those in male rats. The clearance rate of ZCY-15 in female rats was lower than that in male rats. The results confirmed that there were gender differences. It has been shown that ZCY-15 could pass through the blood-brain barrier and was highly concentrated in the hippocampus. We established the first bioanalytical method to quantify ZCY-15 in rodent bio-samples for ongoing pharmacokinetic and tissue distribution studies, and the results were expected to lay foundation for the subsequent studies.

Natural Compounds for the Prevention and Treatment of Cardiovascular and Neurodegenerative Diseases

Secondary metabolites from plants and fungi are stimulating growing interest in consumers and, consequently, in the food and supplement industries. The beneficial effects of these natural compounds are being thoroughly studied and there are frequent updates about the biological activities of old and new molecules isolated from plants and fungi. In this article, we present a review of the most recent literature regarding the recent discovery of secondary metabolites through isolation and structural elucidation, as well as the in vitro and/or in vivo evaluation of their biological effects. In particular, the possibility of using these bioactive molecules in the prevention and/or treatment of widely spread pathologies such as cardiovascular and neurodegenerative diseases is discussed.

Recent Progress in Amaryllidaceae Biotechnology

Plants belonging to the monocotyledonous Amaryllidaceae family include about 1100 species divided among 75 genera. They are well known as medicinal and ornamental plants, producing pharmaceutically important alkaloids, the most intensively investigated of which are galanthamine and lycorine. Amaryllidaceae alkaloids possess various biological activities, the most important one being their anti-acetylcholinesterase activity, used for the treatment of Alzheimer's disease. Due to increased demand for Amaryllidaceae alkaloids (mainly galanthamine) and the limited availability of plant sources, in vitro culture technology has attracted the attention of researchers as a prospective alternative for their sustainable production. Plant in vitro systems have been extensively used for continuous, sustainable, and economically viable production of bioactive plant secondary metabolites. Over the past two decades, a significant success has been demonstrated in the development of in vitro systems synthesizing Amaryllidaceae alkaloids. The present review discusses the state of the art of in vitro Amaryllidaceae alkaloids production, summarizing recently documented plant in vitro systems producing them, as well as the authors' point of view on the development of biotechnological production processes with a focus on the future prospects of in vitro culture technology for the commercial production of these valuable alkaloids.

Arylaminopropanone Derivatives as Potential Cholinesterase Inhibitors: Synthesis, Docking Study and Biological Evaluation

Neurodegenerative diseases in which the decrease of the acetylcholine is observed are growing worldwide. In the present study, a series of new arylaminopropanone derivatives with N-phenylcarbamate moiety (1–16) were prepared as potential acetylcholinesterase and butyrylcholinesterase inhibitors. In vitro enzyme assays were performed; the results are expressed as a percentage of inhibition and the IC₅₀ values. The inhibitory activities were compared with reference drugs galantamine and rivastigmine showing piperidine derivatives (1–3) as the most potent. A possible mechanism of action for these compounds was determined from a molecular modelling study by using combined techniques of docking, molecular dynamics simulations and quantum mechanics calculations.

Impact of modulation of the α7 nicotinic acetylcholine receptor on nicotine reward in the mouse conditioned place preference test

RATIONALE

The α7 nicotinic acetylcholine receptor (nAChR) has been implicated as a target in modulating nicotine reward. However, the effect of pharmacological agents that have been shown to alter the channel properties of the α7 nAChR is not well understood in nicotine reward.

OBJECTIVES

This study aimed to investigate the impact of α7 nAChR pharmacological modulation on nicotine conditioned place preference (CPP) in mice by using positive allosteric modulators (PAMs) and a silent agonist.

METHODS

The effect of the orthosteric α7 nAChR full agonist PNU282987 (1.3 and 9 mg/kg, s.c.), Type I α7 PAM NS1738 (1 and 10 mg/kg; i.p.), the Type II α7 PAM PNU120596 (0.3, 1, and 3 mg/kg, i.p.), and the α7 silent agonist NS6740 (1 and 3 mg/kg, i.p) on nicotine CPP was measured in mice. Mice were conditioned with either saline or nicotine (0.5 mg/kg) for 3 days in the CPP paradigm.

RESULTS

The α7 full orthosteric agonist PNU282987 and the Type II α7 nAChR PAM PNU120596 reduced nicotine CPP, while the silent agonist NS6740 and Type I PAM NS1738 had no effect. The effects of PNU282987 and PNU120596 did not have an effect on morphine CPP.

CONCLUSIONS

Taken together, our results suggest that modulation of the α7 nAChR can play important roles in nicotine CPP in mice. In addition, the Type II α7 nAChR PAM PNU120596 attenuated nicotine reward suggesting that endogenous acetylcholine/choline tone is sufficient to reduce nicotine CPP. These findings highlight a beneficial effect of using α7 nAChR PAMs in nicotine reward.

Anti-Acetylcholinesterase Activities of Mono-Herbal Extracts and Exhibited Synergistic Effects of the Phytoconstituents: A Biochemical and Computational Study

Alzheimer’s disease (AD), a neurodegenerative disease, is the most common form of dementia. Inhibition of acetylcholinesterase (AChE) is a common strategy for the treatment of AD. In this study, aqueous, hydro-methanolic, and methanolic extracts of five potent herbal extracts were tested for their in vitro anti-AChE activity. Among all, the Tinospora cordifolia (Giloy) methanolic fraction performed better with an IC₅₀ of 202.64 µg/mL. Of the HPLC analyzed components of T. cordifolia (methanolic extract), palmatine and berberine performed better (IC₅₀ 0.66 and 0.94 µg/mL, respectively) as compared to gallic acid and the tool compound “galantamine hydrobromide” (IC₅₀ 7.89 and 1.45 µg/mL, respectively). Mode of inhibition of palmatine and berberine was non-competitive, while the mode was competitive for the tool compound. Combinations of individual alkaloids palmatine and berberine resulted in a synergistic effect for AChE inhibition. Therefore, the AChE inhibition by the methanolic extract of T. cordifolia was probably due to the synergism of the isoquinoline alkaloids. Upon molecular docking, it was observed that palmatine and berberine preferred the peripheral anionic site (PAS) of AChE, with π-interactions to PAS residue Trp286, indicating that it may hinder the substrate binding by partially blocking the entrance of the gorge of the active site or the product release.

Natural products and their derivatives as multifunctional ligands against Alzheimer's disease

Alzheimer's disease (AD), a complex neurodegenerative disorder causing multiple cellular changes including impaired cholinergic system, beta-amyloid (βA) aggregation, tau hyperphosphorylation, metal dyshomeostasis, neuroinflammation, and many other pathways are involved in the pathogenesis of the disease. However, the exact cause of the disease is not known. Natural products such as flavonoids, alkaloids, resveratrol, and curcumin have multifunctional properties, and have drawn the attention of the researchers because these molecules are capable of interacting concurrently with the multiple targets of AD. Therefore, natural products and their derivatives with proven efficacy could be used in the management of the neurodegenerative disorders. This review focuses on the natural product based multitarget directed ligands like tacrine-coumarin, tacrine-huperzine A, harmine-isoxazoline, berberine-thiophenyl, galantamine-indole, pyridoxine-resveratrol, donepezil-curcumin and their mode of action.

Amaryllidaceae alkaloids: identification and partial characterization of montanine production in Rhodophiala bifida plant

Rhodophiala bifida (R. bifida) is a representative of the Amaryllidaceae plant family and is rich in montanine, an alkaloid with high pharmaceutical potential. Despite the interest in these compounds, many steps of the biosynthetic pathway have not been elucidated. In this study, we identified the alkaloids produced in different organs of R. bifida under different growth conditions, set up the conditions for in vitro R. bifida regeneration and initiated the molecular characterization of two R. bifida genes involved in alkaloids biosynthesis: the Norbelladine 4'-O-Methyltransferase (RbN4OMT) and the Cytochrome P450 (RbCYP96T). We show that montanine is the main alkaloid produced in the different R. bifida organs and developed a direct organogenesis regeneration protocol, using twin-scale explants cultivated on media enriched with naphthalene acetic acid and benzyladenine. Finally, we analyzed the RbN4OMT and RbCYP96T gene expressions in different organs and culture conditions and compared them to alkaloid production. In different organs of R. bifida young, adult and regenerated plants, as well as under various growing conditions, the transcripts accumulation was correlated with the production of alkaloids. This work provides new tools to improve the production of this important pharmaceutical compound and for future biotechnological studies.

Clinanthus microstephium, an Amaryllidaceae Species with Cholinesterase Inhibitor Alkaloids: Structure-Activity Analysis of Haemanthamine Skeleton Derivatives

Plants of the Amaryllidaceae family are well-known (not only) for their ornamental value but also for the alkaloids that they produce. In this report, the first phytochemical study of Clinanthus genus was carried out. The chemical composition of alkaloid fractions from Clinanthus microstephium was analyzed by GC/MS and NMR. Seven known compounds belonging to three structural types of Amaryllidaceae alkaloids were identified. An epimeric mixture of a haemanthamine-type compound (6-hydroxymaritidine) was tested as an inhibitor against acetyl- and butyrylcholinesterase enzymes (AChE and BChE, respectively), two enzymes relevant in the treatment of Alzheimer's disease, with good results. Structure-activity relationships through molecular docking studies with this alkaloid and other structurally related compounds were discussed.

Neurobiological and Neurophysiological Mechanisms Underlying Nicotine Seeking and Smoking Relapse

Tobacco-related morbidity and mortality continue to be a significant public health concern. Unfortunately, current FDA-approved smoking cessation pharmacotherapies have limited efficacy and are associated with high rates of relapse. Therefore, a better understanding of the neurobiological and neurophysiological mechanisms that promote smoking relapse is needed to develop novel smoking cessation medications. Here, we review preclinical studies focused on identifying the neurotransmitter and neuromodulator systems that mediate nicotine relapse, often modeled in laboratory animals using the reinstatement paradigm, as well as the plasticity-dependent neurophysiological mechanisms that facilitate nicotine reinstatement. Particular emphasis is placed on how these neuroadaptations relate to smoking relapse in humans. We also highlight a number of important gaps in our understanding of the neural mechanisms underlying nicotine reinstatement and critical future directions, which may lead toward the development of novel, target pharmacotherapies for smoking cessation.

Plants-Derived Neuroprotective Agents: Cutting the Cycle of Cell Death through Multiple Mechanisms

Neuroprotection is the preservation of the structure and function of neurons from insults arising from cellular injuries induced by a variety of agents or neurodegenerative diseases (NDs). The various NDs including Alzheimer's, Parkinson's, and Huntington's diseases as well as amyotropic lateral sclerosis affect millions of people around the world with the main risk factor being advancing age. Each of these diseases affects specific neurons and/or regions in the brain and involves characteristic pathological and molecular features. Hence, several in vitro and in vivo study models specific to each disease have been employed to study NDs with the aim of understanding their underlying mechanisms and identifying new therapeutic strategies. Of the most prevalent drug development efforts employed in the past few decades, mechanisms implicated in the accumulation of protein-based deposits, oxidative stress, neuroinflammation, and certain neurotransmitter deficits such as acetylcholine and dopamine have been scrutinized in great detail. In this review, we presented classical examples of plant-derived neuroprotective agents by highlighting their structural class and specific mechanisms of action. Many of these natural products that have shown therapeutic efficacies appear to be working through the above-mentioned key multiple mechanisms of action.

Neurologically Potent Molecules from Crataegus oxyacantha; Isolation, Anticholinesterase Inhibition, and Molecular Docking

Crataegus oxyacantha is an important herbal supplement and famous for its antioxidant potential. The antioxidant in combination with anticholinesterase activity can be considered as an important target in the management of Alzheimer’s disease. The compounds isolated from C. oxyacantha were evaluated for cholinesterases inhibitory activity using Ellman’s assay with Galantamine as standard drug. Total of nine (1–9) compounds were isolated. Compounds 1 and 2 were isolated for the first time from natural source. Important natural products like β-Sitosterol-3-O-β-D-Glucopyranoside (3), lupeol (4), β-sitosterol (5), betulin (6), betulinic acid (7), oleanolic acid (8), and chrysin (9) have also been isolated from C. oxyacantha. Overall, all the compounds exhibited an overwhelming acetylcholinesterase (AChE) inhibition potential in the range 5.22–44.47 μM. The compound 3 was prominent AChE inhibitor with IC₅₀ value of 5.22 μM. Likewise, all the compounds were also potent in butyrylcholinesterase (BChE) inhibitions with IC₅₀s of up to 0.55–15.36 μM. All the compounds, except 3, were selective toward BChE. Mechanism of the inhibition of both the enzymes were further studied by docking procedures using Genetic Optimization for Ligand Docking suit v5.4.1. Furthermore, computational blood brain barrier prediction of the isolated compounds suggest that these are BBB+.

Transcriptome Analysis of Secondary Metabolism Pathway, Transcription Factors, and Transporters in Response to Methyl Jasmonate in Lycoris aurea

Lycoris aurea, a medicinal species of the Amaryllidaceae family, is used in the practice of traditional Chinese medicine (TCM) because of its broad pharmacological activities of Amaryllidaceae alkaloids. Despite the officinal and economic importance of Lycoris species, the secondary mechanism for this species is relatively deficient. In this study, we attempted to characterize the transcriptome profiling of L. aurea seedlings with the methyl jasmonate (MeJA) treatment to uncover the molecular mechanisms regulating plant secondary metabolite pathway. By using short reads sequencing technology (Illumina), two sequencing cDNA libraries prepared from control (Con) and 100 μM MeJA-treated (MJ100) samples were sequenced. A total of 26,809,842 and 25,874,478 clean reads in the Con and MJ100 libraries, respectively, were obtained and assembled into 59,643 unigenes. Among them, 41,585 (69.72%) unigenes were annotated by basic local alignment search tool similarity searches against public sequence databases. These included 55 Gene Ontology (GO) terms, 128 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and 25 Clusters of Orthologous Groups (COG) families. Additionally, 4,175 differentially expressed genes (DEGs; false discovery rate ≤ 0.001 and |log₂ Ratio| ≥ 1) with 2,291 up-regulated and 1,884 down-regulated, were found to be affected significantly under MeJA treatment. Subsequently, the DEGs encoding key enzymes involving in the secondary metabolite biosynthetic pathways, transcription factors, and transporter proteins were also analyzed and summarized. Meanwhile, we confirmed the altered expression levels of the unigenes that encode transporters and transcription factors using quantitative real-time PCR (qRT-PCR). With this transcriptome sequencing, future genetic and genomics studies related to the molecular mechanisms associated with the chemical composition of L. aurea may be improved. Additionally, the genes involved in the enrichment of secondary metabolite biosynthesis-related pathways could enhance the potential applications of L. aurea.

Current Treatment Options for Alzheimer's Disease and Parkinson's Disease Dementia

Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most common neurodegenerative disorders encountered in clinical practice. Whilst dementia has long been synonymous with AD, it is becoming more widely accepted as part of the clinical spectrum in PD (PDD). Neuropsychiatric complications, including psychosis, mood and anxiety disorders, and sleep disorders also frequently co-exist with cognitive dysfunctions in AD and PDD patients. The incidence of such symptoms is often a significant source of disability, and may aggravate pre-existing cognitive deficits. Management of AD and PDD involves both pharmacological and non-pharmacological measures. Although research on pharmacological therapies for AD and PDD has so far had some success in terms of developing symptomatic treatments, the benefits are often marginal and non-sustained. These shortcomings have led to the investigation of non-pharmacological and novel treatments for both AD and PD. Furthermore, in light of the diverse constellation of other neuropsychiatric, physical, and behavioural symptoms that often occur in AD and PD, consideration needs to be given to the potential side effects of pharmacological treatments where improving one symptom may lead to the worsening of another, rendering the clinical management of these patients challenging. Therefore, the present article will critically review the evidence for both pharmacological and non-pharmacological treatments for cognitive impairment in AD and PD patients. Treatment options for other concomitant neuropsychiatric and behavioural symptoms, as well as novel treatment strategies will also be discussed.

Repeated administration of an acetylcholinesterase inhibitor attenuates nicotine taking in rats and smoking behavior in human smokers

Tobacco smoking remains the leading cause of preventable death worldwide and current smoking cessation medications have limited efficacy. Thus, there is a clear need for translational research focused on identifying novel pharmacotherapies for nicotine addiction. Our previous studies demonstrated that acute administration of an acetylcholinesterase inhibitor (AChEI) attenuates nicotine taking and seeking in rats and suggest that AChEIs could be repurposed for smoking cessation. Here, we expand upon these findings with experiments designed to determine the effects of repeated AChEI administration on voluntary nicotine taking in rats as well as smoking behavior in human smokers. Rats were trained to self-administer intravenous infusions of nicotine (0.03 mg kg(-1) per 0.59 ml) on a fixed-ratio-5 schedule of reinforcement. Once rats maintained stable nicotine taking, galantamine or donepezil was administered before 10 consecutive daily nicotine self-administration sessions. Repeated administration of 5.0 mg kg(-1) galantamine and 3.0 mg kg(-1) donepezil attenuated nicotine self-administration in rats. These effects were reinforcer-specific and not due to adverse malaise-like effects of drug treatment as repeated galantamine and donepezil administration had no effects on sucrose self-administration, ad libitum food intake and pica. The effects of repeated galantamine (versus placebo) on cigarette smoking were also tested in human treatment-seeking smokers. Two weeks of daily galantamine treatment (8.0 mg (week 1) and 16.0 mg (week 2)) significantly reduced smoking rate as well as smoking satisfaction and reward compared with placebo. This translational study indicates that repeated AChEI administration reduces nicotine reinforcement in rats and smoking behavior in humans at doses not associated with tolerance and/or adverse effects.

Plant alkaloids as drug leads for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative illness associated with dementia and is most prevalent among the elderly population. Current medications can only treat symptoms. Alkaloids are structurally diverse and have been an important source of therapeutics for various brain disorders. Two US Food and Drug Administration (FDA)-approved acetylcholinesterase inhibitors for AD, galantamine and rivastigmine, are in fact alkaloids. In addition, clinical trials of four other extensively studied alkaloids-huperzine A, caffeine, nicotine, and indomethacin-have been conducted but do not convincingly demonstrate their clinical efficacy for AD. Interestingly, rhynchophylline, a known neuroprotective alkaloid, was recently discovered by in silico screening as an inhibitor of EphA4, a novel target for AD. Here, we review the pathophysiological mechanisms underlying AD, current treatment strategies, and therapeutic potential of several selected plant alkaloids in AD, highlighting their various drug targets and the key supportive preclinical and clinical studies. Future research should include more rigorous clinical studies of the most promising alkaloids, the further development of recently discovered candidate alkaloids, and the continual search for new alkaloids for relevant drug targets. It remains promising that an alkaloid drug candidate could significantly affect the progression of AD in addition to providing symptomatic relief.

Formulation and evaluation of galantamine gel as drug reservoir in transdermal patch delivery system

Galantamine hydrobromide is formulated in tablets and capsules prescribed through oral delivery for the treatment of Alzheimer's disease. However, oral delivery of drugs can cause severe side effects such as nausea, vomiting, and gastrointestinal disturbance. Transdermal delivery of galantamine hydrobromide could avoid these unwanted side effects. In this work, galantamine hydrobromide was formulated in gel drug reservoir which was then fabricated in the transdermal patch. The in vitro drug release studies revealed that the drug release from the donor chamber to receptor chamber of Franz diffusion cell was affected by the amount of polymer, amount of neutralizer, amount of drug, types of permeation enhancer, and amount of permeation enhancer. Visual observations of the gels showed that all formulated gels are translucent, homogeneous, smooth, and stable. These gels have pH in the suitable range for skin. The gel also showed high drug content uniformity. Hence, this formulation can be further used in the preparation of transdermal patch drug delivery system.

Nicotinic receptor modulation to treat alcohol and drug dependence

Alcohol and drug dependence are serious public health problems worldwide. The prevalence of alcohol and drug dependence in the United States and other parts of the world is significant. Given the limitations in the efficacy of current pharmacotherapies to treat these disorders, research in developing alternative pharmacotherapies continues. Preclinical and clinical evidence thus far has indicated that brain nicotinic acetylcholine receptors (nAChRs) are important pharmacological targets for the development of medications to treat alcohol and drug dependence. The nAChRs are a super family of ligand gated ion channels, and are expressed throughout the brain with twelve neuronal nAChR subunits (α2–α10 and β2–β4) identified. Here, we review preclinical and clinical evidence involving a number of nAChR ligands that target different nAChR subtypes in alcohol and nicotine addiction. The important ligands include cytisine, lobeline, mecamylamine, varenicline, sazetidine A and others that target α4β2^* nAChR subtypes as small molecule modulators of the brain nicotinic cholinergic system are also discussed. Taken together, both preclinical and clinical data exist that support nAChR–based ligands as promising therapeutic agents for the treatment of alcohol and drug dependence.

Mechanistic Insights to the Cytotoxicity of Amaryllidaceae Alkaloids

With over 500 individual compounds, the Amaryllidaceae alkaloids represent a large and structurally diverse group of phytochemicals. Coupled to this structural diversity is the significant array of biological properties manifested by many of its members, of which their relevance in motor neuron disease and cancer chemotherapy has attracted considerable attention. To this extent, galanthamine has evolved into a successful commercial drug for Alzheimer's disease since its approval by the FDA in 2001. Concurrently, there have been several positive indicators for the emergence of an anticancer drug from the Amaryllidaceae due to the potency of several of its representatives as cell line specific antiproliferative agents. In this regard, the phenanthridones such as pancratistatin and narciclasine have offered most promise since their advancement into clinical trials, following which there has been renewed interest in the cytotoxic properties of these alkaloids. Given this background, this review seeks to highlight the various mechanisms which have been invoked to corroborate the cytotoxic effects of Amaryllidaceae alkaloids.

Donepezil, an acetylcholinesterase inhibitor, attenuates nicotine self-administration and reinstatement of nicotine seeking in rats

Nicotine craving and cognitive impairments represent core symptoms of nicotine withdrawal and predict relapse in abstinent smokers. Current smoking cessation pharmacotherapies have limited efficacy in preventing relapse and maintaining abstinence during withdrawal. Donepezil is an acetylcholinesterase inhibitor that has been shown previously to improve cognition in healthy non-treatment-seeking smokers. However, there are no studies examining the effects of donepezil on nicotine self-administration and/or the reinstatement of nicotine-seeking behavior in rodents. The present experiments were designed to determine the effects of acute donepezil administration on nicotine taking and the reinstatement of nicotine-seeking behavior, an animal model of relapse in abstinent human smokers. Moreover, the effects of acute donepezil administration on sucrose self-administration and sucrose seeking were also investigated in order to determine whether donepezil's effects generalized to other reinforced behaviors. Acute donepezil administration (1.0 or 3.0 mg/kg, i.p.) attenuated nicotine, but not sucrose self-administration maintained on a fixed-ratio 5 schedule of reinforcement. Donepezil administration also dose-dependently attenuated the reinstatement of both nicotine- and sucrose-seeking behaviors. Commonly reported adverse effects of donepezil treatment in humans are nausea and vomiting. However, at doses required to attenuate nicotine self-administration in rodents, no effects of donepezil on nausea/malaise as measured by pica were observed. Collectively, these results indicate that increased extracellular acetylcholine levels are sufficient to attenuate nicotine taking and seeking in rats and that these effects are not due to adverse malaise symptoms such as nausea.

Traditional usage, phytochemistry and pharmacology of the South African medicinal plant Boophone disticha (L.f.) Herb. (Amaryllidaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Boophone disticha is the most common member of the South African Amaryllidaceae used extensively in traditional medicine of the various indigenous population groups, including the Sotho, Xhosa and Zulu as well as the San. This survey was carried out to identify and highlight areas relevant to the traditional usage of Boophone disticha. Pharmacological aspects were examined with the purpose of reconciling these with the traditional usage of the plant. In relation to phytochemical make-up, particular attention was paid on how its alkaloid constitution might corroborate the various biological effects manifested by the plant.

MATERIALS AND METHODS

Information gathering involved the use of four different database platforms, including Google Scholar, ScienceDirect, SciFinder(®) and Scopus. Arrangement and detailing of this information is as reflected in the various sections of the paper.

RESULTS

Sixteen categories were identified under which Boophone disticha finds use in traditional medicine. These were shown to include general usage purposes, such as 'cultural and dietary', 'well-being', 'personal injury', 'divinatory purposes', 'psychoactive properties' and 'veterinary uses'. Furthermore, traditional usage was seen to involve six body systems, including functions pertaining to the circulatory, gastrointestinal, muscular, neurological, respiratory and urinary systems. The four remaining categories relate to use for inflammatory conditions, cancer, malaria and tuberculosis. Overall, three areas were discernible in which Boophone disticha finds most usage, which are (i) ailments pertaining to the CNS, (ii) wounds and infections, and (iii) inflammatory conditions. In addition, several aspects pertaining to the toxic properties of the plant are discussed, including genotoxicity, mutagenicity and neurotoxicity.

CONCLUSION

The widespread ethnic usage of Boophone disticha has justified its standing as a flagship for the Amaryllidaceae and its relevance to South African traditional medicine. Furthermore, its promising pharmacological and phytochemical profiles have stimulated significant interest in the clinical realm, especially in the areas of cancer and motor neuron disease chemotherapy. These collective properties should prove useful in steering the progress of the plant towards a wider audience.

Pharmacological and toxicological insights to the South African Amaryllidaceae

The plant family Amaryllidaceae is of provenance in the South African region which is known to harbor about a third of the global complement of around 1000 species. It has widespread usage in the traditional medicinal practices of the indigenous peoples of the region. As a consequence and given its unique alkaloid principles, its members have provided a viable platform for phytochemical based drug discovery. The medicinal potential of the family has been realized through the commercialization of galanthamine as an Alzheimer's drug due to its potent and selective inhibitory activity against the enzyme acetylcholinesterase. Further promising chemotherapeutic candidates of the family reside with the phenanthridone class of alkaloids such as pancratistatin which exhibit potent and cell line specific antiproliferative properties with significant potential for clinical development. Despite these interesting medicinal attributes, plants of the Amaryllidaceae are known to be poisonous and several of them have been classified as such. This survey taking into consideration Amaryllidaceae plants native to South Africa aims to strike a balance between the medicinal potential of the family on one hand and its adverse and toxic effects on the other.

Cellular, molecular, and genetic substrates underlying the impact of nicotine on learning

Addiction is a chronic disorder marked by long-lasting maladaptive changes in behavior and in reward system function. However, the factors that contribute to the behavioral and biological changes that occur with addiction are complex and go beyond reward. Addiction involves changes in cognitive control and the development of disruptive drug-stimuli associations that can drive behavior. A reason for the strong influence drugs of abuse can exert on cognition may be the striking overlap between the neurobiological substrates of addiction and of learning and memory, especially areas involved in declarative memory. Declarative memories are critically involved in the formation of autobiographical memories, and the ability of drugs of abuse to alter these memories could be particularly detrimental. A key structure in this memory system is the hippocampus, which is critically involved in binding multimodal stimuli together to form complex long-term memories. While all drugs of abuse can alter hippocampal function, this review focuses on nicotine. Addiction to tobacco products is insidious, with the majority of smokers wanting to quit; yet the majority of those that attempt to quit fail. Nicotine addiction is associated with the presence of drug-context and drug-cue associations that trigger drug seeking behavior and altered cognition during periods of abstinence, which contributes to relapse. This suggests that understanding the effects of nicotine on learning and memory will advance understanding and potentially facilitate treating nicotine addiction. The following sections examine: (1) how the effects of nicotine on hippocampus-dependent learning change as nicotine administration transitions from acute to chronic and then to withdrawal from chronic treatment and the potential impact of these changes on addiction, (2) how nicotine usurps the cellular mechanisms of synaptic plasticity, (3) the physiological changes in the hippocampus that may contribute to nicotine withdrawal deficits in learning, and (4) the role of genetics and developmental stage (i.e., adolescence) in these effects.

Alkaloids as a source of potential anticholinesterase inhibitors for the treatment of Alzheimer's disease

Objectives

The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is currently the main pharmacological strategy available for Alzheimer's disease (AD). In this sense, many alkaloids isolated from natural sources, such as physostigmine, have been long recognized as acetyl- and butyrylcholinesterase (BChE) inhibitors. Since the approval of galantamine for the treatment of AD patients, the search for new anticholinesterase alkaloids has escalated, leading to promising candidates such as huperzine A. This review aims to summarize recent advances in current knowledge on alkaloids as AChE and BChE inhibitors, highlighting structure–activity relationship (SAR) and docking studies.

Key findings

Natural alkaloids belonging to the steroidal/triterpenoidal, quinolizidine, isoquinoline and indole classes, mainly distributed within Buxaceae, Amaryllidaceae and Lycopodiaceae, are considered important sources of alkaloids with anti-enzymatic properties. Investigations into the possible SARs for some active compounds are based on molecular modelling studies, predicting the mode of interaction of the molecules with amino acid residues in the active site of the enzymes. Following this view, an increasing interest in achieving more potent and effective analogues makes alkaloids good chemical templates for the development of new cholinesterase inhibitors.

Summary

The anticholinesterase activity of alkaloids, together with their structural diversity and physicochemical properties, makes them good candidate agents for the treatment of AD.

Molecular recognition of rosmarinic acid from Salvia sclareoides extracts by acetylcholinesterase: a new binding site detected by NMR spectroscopy

Acetylcholinesterase (AChE) inhibition is one of the most currently available therapies for the management of Alzheimer's disease (AD) symptoms. In this context, NMR spectroscopy binding studies were accomplished to explain the inhibition of AChE activity by Salvia sclareoides extracts. HPLC-MS analyses of the acetone, butanol and water extracts eluted with methanol and acidified water showed that rosmarinic acid is present in all the studied samples and is a major constituent of butanol and water extracts. Moreover, luteolin 4'-O-glucoside, luteolin 3',7-di-O-glucoside and luteolin 7-O-(6''-O-acetylglucoside) were identified by MS(2) and MS(3) data acquired during the LC-MS(n) runs. Quantification of rosmarinic acid by HPLC with diode-array detection (DAD) showed that the butanol extract is the richest one in this component (134 μg mg(-1) extract). Saturation transfer difference (STD) NMR spectroscopy binding experiments of S. sclareoides crude extracts in the presence of AChE in buffer solution determined rosmarinic acid as the only explicit binder for AChE. Furthermore, the binding epitope and the AChE-bound conformation of rosmarinic acid were further elucidated by STD and transferred NOE effect (trNOESY) experiments. As a control, NMR spectroscopy binding experiments were also carried out with pure rosmarinic acid, thus confirming the specific interaction and inhibition of this compound against AChE. The binding site of AChE for rosmarinic acid was also investigated by STD-based competition binding experiments using Donepezil, a drug currently used to treat AD, as a reference. These competition experiments demonstrated that rosmarinic acid does not compete with Donepezil for the same binding site. A 3D model of the molecular complex has been proposed. Therefore, the combination of the NMR spectroscopy based data with molecular modelling has permitted us to detect a new binding site in AChE, which could be used for future drug development.

Cytotoxic Agents of the Crinane Series of Amaryllidaceae Alkaloids

In the alkaloid galanthamine, the plant family Amaryllidaceae has endowed the pharmaceutical community with a potent and selective inhibitor of the enzyme acetylcholinestersae (AChE), of prominence in the chemotherapeutic approach towards motor neuron diseases. Following on the commercial success of this prescription drug in the treatment of Alzheimer's disease, it is anticipated that other drug candidates will in future emerge from the family. In this regard, the phenanthridones, exemplified by narciclasine and pancratistatin, of the lycorine series of Amaryllidaceae alkaloids have shown much promise as remarkably potent and selective anticancer agents, with a drug target of the series destined for the clinical market within the next decade. Given these interesting biological properties and their natural abundance, plants of the Amaryllidaceae have provided a diverse and accessible platform for phytochemical-based drug discovery. The crinane series of Amaryllidaceae alkaloids are also enriched with a significant array of biological properties. As a consequence of their close structural similarity to the anticancer agents of the lycorine series, the cytotoxic potential of crinane alkaloids has been realized through structure-activity relationship (SAR) studies involving targets of both semi-synthetic and natural origin, which has identified several members as leads with promising antiproliferative profiles. As the first of its kind, this review seeks to collate such information from the past few decades in advancing the crinane group as a viable platform for anticancer drug discovery.

De novo sequence assembly and characterization of Lycoris aurea transcriptome using GS FLX titanium platform of 454 pyrosequencing

Background

Lycoris aurea, also called Golden Magic Lily, is an ornamentally and medicinally important species of the Amaryllidaceae family. To date, the sequencing of its whole genome is unavailable as a non-model organism. Transcriptomic information is also scarce for this species. In this study, we performed de novo transcriptome sequencing to produce the first comprehensive expressed sequence tag (EST) dataset for L. aurea using high-throughput sequencing technology.

Methodology and Principal Findings

Total RNA was isolated from leaves with sodium nitroprusside (SNP), salicylic acid (SA), or methyl jasmonate (MeJA) treatment, stems, and flowers at the bud, blooming, and wilting stages. Equal quantities of RNA from each tissue and stage were pooled to construct a cDNA library. Using 454 pyrosequencing technology, a total of 937,990 high quality reads (308.63 Mb) with an average read length of 329 bp were generated. Clustering and assembly of these reads produced a non-redundant set of 141,111 unique sequences, comprising 24,604 contigs and 116,507 singletons. All of the unique sequences were involved in the biological process, cellular component and molecular function categories by GO analysis. Potential genes and their functions were predicted by KEGG pathway mapping and COG analysis. Based on our sequence analysis and published literatures, many putative genes involved in Amaryllidaceae alkaloids synthesis, including PAL, TYDC OMT, NMT, P450, and other potentially important candidate genes, were identified for the first time in this Lycoris. Furthermore, 6,386 SSRs and 18,107 high-confidence SNPs were identified in this EST dataset.

Conclusions

The transcriptome provides an invaluable new data for a functional genomics resource and future biological research in L. aurea. The molecular markers identified in this study will provide a material basis for future genetic linkage and quantitative trait loci analyses, and will provide useful information for functional genomic research in future.

Positive allosteric modulator of α7 nicotinic-acetylcholine receptors, PNU-120596 augments the effects of donepezil on learning and memory in aged rodents and non-human primates

The development of novel therapeutic agents for disorders of cognition such as Alzheimer's disease (AD) is of paramount importance given the ever-increasing elderly population, however; there is also considerable interest in any strategy that might enhance the clinical efficacy of currently available treatments. The purpose of this study was to evaluate an adjunctive treatment strategy to memory enhancement, namely combining the commonly prescribed acetylcholinesterase inhibitor (AChEI) donepezil, with a positive allosteric modulator (PAM) of α7 nicotinic-acetylcholine receptors (α7-nAChRs), PNU-120596. The treatment strategy was evaluated in a (non-spatial) spontaneous novel object recognition (NOR) task in young rats; a water maze spatial learning and recall procedure in aged, cognitively-impaired rats, and a delayed match to sample (working/short term memory) task in aged rhesus monkeys. In all three experiments a similar drug response was observed, namely that donepezil administered alone improved task performance in a dose-dependent manner; that PNU-120596 administered alone was without significant effect, but that the combination of PNU-120596 with a subthreshold dose of donepezil was effective. The positive effect of the drug combination appeared to be α7-nAChR mediated given that it was blocked in the NOR task by the selective α7-nAChR antagonist methyllycaconitine (MLA). Collectively, these data indicate that PNU-120596 increases the effective dose range of donepezil in learning/memory-related tasks in young and age-impaired animal models. The results suggest that α7-nAChR-selective PAMs like PNU-120596 have potential as adjunctive treatments with acetylcholinesterase inhibitors (e.g., donepezil) for age-related illnesses such as AD as well memory disorders not necessarily associated with advanced age.

Cytotoxic Agents of the Crinane Series of Amaryllidaceae Alkaloids

In the alkaloid galanthamine, the plant family Amaryllidaceae has endowed the pharmaceutical community with a potent and selective inhibitor of the enzyme acetylcholinestersae (AChE), of prominence in the chemotherapeutic approach towards motor neuron diseases. Following on the commercial success of this prescription drug in the treatment of Alzheimer's disease, it is anticipated that other drug candidates will in future emerge from the family. In this regard, the phenanthridones, exemplified by narciclasine and pancratistatin, of the lycorine series of Amaryllidaceae alkaloids have shown much promise as remarkably potent and selective anticancer agents, with a drug target of the series destined for the clinical market within the next decade. Given these interesting biological properties and their natural abundance, plants of the Amaryllidaceae have provided a diverse and accessible platform for phytochemical-based drug discovery. The crinane series of Amaryllidaceae alkaloids are also enriched with a significant array of biological properties. As a consequence of their close structural similarity to the anticancer agents of the lycorine series, the cytotoxic potential of crinane alkaloids has been realized through structure-activity relationship (SAR) studies involving targets of both semi-synthetic and natural origin, which has identified several members as leads with promising antiproliferative profiles. As the first of its kind, this review seeks to collate such information from the past few decades in advancing the crinane group as a viable platform for anticancer drug discovery.

A critical review of cholinesterase inhibitors as a treatment modality in Alzheimer's disease

Early research into Alzheimer's disease launched the cholinergic hypothesis, based on the correlation between central cholinergic deficiency and clinical measures of cognitive decline. This was epitomized in therapeutic strategies employing a variety of procholinergic agents, of which only the inhibitors of cholinesterase (ChE), the enzyme thai hydrolyzes acetylcholine in the synaptic cleft, have been proven clinically viable. Five such agents are reviewed: tacrine and donepezil, which act at the ionic subsite of acetylcholinesterase (AChE), and rivastigmine, galantamine, and metrifonate, which act at its catalytic esteratic subsite. Despite statistical evidence of efficacy from numerous well-controlled multicenter trials, important clinical utility issues remain outstanding: (i) number-needed-to-treat (NNT) analyses, quantifying the number of patients needing to be treated for one patient to show benefit, find values of 3 to 20; (ii) the pivotal trials themselves were conducted in nonrepreseniative populations, largely comprised of physically healthy outpatients with mildto-moderate Alzheimer's disease and a mean age of 72 years (thereby excluding over 30% of typical Alzheimer patients in State of California-funded clinics), treated for up to 6 months; and (Hi) tolerability is underreported and characterized by a positive correlation between dose, effect and cholinergic side effects - potentially serious adverse events include bradycardia, anorexia, weight loss and myasthenia with respiratory depression. Therapies thus require titration and constant monitoring. Nevertheless, acetylcholinesterase inhibitors (AChEls) constitute the first class of effective agents and are likely to remain so in the continuing absence of viable alternatives.

Galantamine, an acetylcholinesterase inhibitor and positive allosteric modulator of nicotinic acetylcholine receptors, attenuates nicotine taking and seeking in rats

Current smoking cessation pharmacotherapies have limited efficacy in preventing relapse and maintaining abstinence during withdrawal. Galantamine is an acetylcholinesterase inhibitor that also acts as a positive allosteric modulator of nicotinic acetylcholine receptors. Galantamine has recently been shown to reverse nicotine withdrawal-induced cognitive impairments in mice, which suggests that galantamine may function to prevent relapse in human smokers. However, there are no studies examining whether galantamine administration modulates nicotine self-administration and/or reinstatement of nicotine seeking in rodents. The present experiments were designed to determine the effects of galantamine administration on nicotine taking and reinstatement of nicotine-seeking behavior, an animal model of relapse. Moreover, the effects of galantamine on sucrose-maintained responding and sucrose seeking were also examined to determine whether galantamine's effects generalized to other reinforced behaviors. An inverted U-shaped dose-response curve was obtained when animals self-administered different unit doses of nicotine with the highest responding for 0.03 mg/kg per infusion of nicotine. Acute galantamine administration (5.0 mg/kg, i.p.) attenuated nicotine self-administration when animals were maintained on either a fixed-ratio 5 (FR5) or progressive ratio (PR) schedule of reinforcement. Galantamine administration also attenuated the reinstatement of nicotine-seeking behavior. No significant effects of galantamine on sucrose self-administration or sucrose reinstatement were noted. Acetylcholinesterase inhibitors have also been shown to produce nausea and vomiting in humans. However, at doses required to attenuate nicotine self-administration, no effects of galantamine on nausea/malaise as measured by pica were noted. These results indicate that increased extracellular acetylcholine levels and/or nicotinic acetylcholine receptor stimulation is sufficient to attenuate nicotine taking and seeking in rats and that these effects are reinforcer selective and not due to adverse malaise symptoms such as nausea.